STP266

    Structural and Lean Mass Concrete as Affected by Water-Reducing, Set-Retarding Agents

    Published: Jan 1960


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    Abstract

    Several commercial water-reducing, set-retarding agents of the lignin and hydroxylated carboxylic acid classes are explored as to their effect on mix design and on the many properties of fresh and hardened concrete. Their benefits and limitations are explained so that the agents may be intelligently and confidently utilized. Methodology consisted of comparing various concretes containing water-reducing retarding agents with similar concretes without agent. Results of several hundred laboratory and field tests conducted over the past 5 years show that optimum dosages of many agents on the market today will increase the compressive, tensile, and shearing strength of mass and structural concrete and improve its resistance to freezing and thawing and sulfate-induced expansive forces. The principal contribution of water-reducing retarding agents toward improved workability is through their ability to extend the length of time in which concrete can be consolidated by vibration and thus reduce the risk of obtaining cold joints. They do not, however, improve the ease of handling concrete as gaged by the slump test, and in a few cases will increase the rate of slump loss. Volume change due to wetting and drying, and permeability of mass concrete are not affected by water-reducing retarding agents in amounts sufficient to warrant changes in design and construction considerations. However, reduced temperature rise and savings in cooling mass concrete may be achieved as a result of lower cement requirement attendant to their use.


    Author Information:

    Wallace, GB
    Engineers, Concrete Laboratory, United States Bureau of Reclamation, Denver, Colo.

    Ore, EL
    Engineers, Concrete Laboratory, United States Bureau of Reclamation, Denver, Colo.


    Paper ID: STP39570S

    Committee/Subcommittee: C09.68

    DOI: 10.1520/STP39570S


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